PROSTHETIC HEART VALVE FLUID MECHANICS AND BLOOD DAMAGE

Summary

Principal Investigator: JOHN TARBELL
Affiliation: City University of New York
Country: USA
Abstract: DESCRIPTION (Provided by Applicant): Mechanical heart valves (MHVS) are widely used for the replacement of natural valves as well as in ventricular assist devices and artificial hearts. Valves can cause blood damage which may lead to hemolysis and thromboembolism. Hemodynamic stresses imposed on blood elements as they pass through the valve play a major role in blood damage. In addition, the formation and collapse of cavitation bubbles near mechanical heart valves at closure have been implicated in both blood element and valve material damage. A related problem is the generation of stable gas bubbles by MHVs which show up as emboli in the cranial circulation and are detected as high intensity transient signals (HITS) in transcranial Doppler diagnostics. In the next grant period we will focus on determining the detailed mechanisms which lead to stable gas bubble formation on current MHVs and measuring the fluid stresses and flow structures very close to the valve housings. This study will provide the basic science required to support the development of a new generation of MHVs with reduced thromboembolic potential. The specific aims of the proposed research are: 1. To observe the formation of stable gas bubbles on MHVs using C02-supplemented test fluids and HSV. Valves with observation windows in their housings will be used to record the bubble formation process at framing rates up to 10000 I sec. An ultrasound Doppler system will be used to quantify stable bubble formation rates. Modified valves (occluder material and gap width) will also be studied and the bubble formation process will be related to the fluid mechanical structures observed under specific aim 2. In this way we will be able to test the hypothesis that vortex structures sustain bubble growth from nuclei generated by cavitation. 2. To determine the near-valve flow characteristics during and shortly after valve closure that are associated with the generation of Stable gas bubbles and elevated turbulent stresses. We will modify existing valves by cutting windows into the metal valve rings (housings) which will allow us to observe and quantify fluid flow structures and turbulence levels very close to the housing where cavitation and stable gas bubble formation are initiated. By retaining most of the valve housing intact, we will not alter the normal valve closing dynamics and energy transfer. We will use LDV and high resolution PIV to assess turbulent stresses and focal flow structures. To further enhance our understanding of mechanisms, we will alter closing dynamics and flow structures by using different disk materials (Delrin and pyrolytic carbon), which are known to alter cavitation potential, as well as valves of the same materials but with different gaps between the occluder housing which are expected to generate different vorticity structures.
Funding Period: 1993-05-01 - 2005-06-30
more information: NIH RePORT

Top Publications

  1. ncbi Near field flow characteristics of the Bjork-Shiley Monostrut valve in a modified single shot valve chamber
    Keefe B Manning
    Department of Bioengineering, The Pennsylvania State University, University Park 16802, USA
    ASAIO J 51:133-8. 2005
  2. ncbi Acoustic and visual characteristics of cavitation induced by mechanical heart valves
    Kwanghyun Sohn
    The Pennsylvania State University, Department of Bioengineering, 205 Hallowell Building, University Park, PA 16802, USA
    J Heart Valve Dis 14:551-8. 2005
  3. ncbi The effect of dissolved carbon dioxide on cavitation intensity in mechanical heart valves
    Luke H Herbertson
    Department of Bioengineering, The Pennsylvania State University, University Park, PA 16802, USA
    J Heart Valve Dis 14:835-42. 2005
  4. ncbi Wavelet transforms in the analysis of mechanical heart valve cavitation
    Luke H Herbertson
    Department of Bioengineering, The Pennsylvania State University, University Park, PA 16802, USA
    J Biomech Eng 128:217-22. 2006
  5. ncbi Modifying a tilting disk mechanical heart valve design to improve closing dynamics
    Luke H Herbertson
    Department of Bioengineering, The Pennsylvania State University, University Park, PA 16802, USA
    J Biomech Eng 130:054503. 2008

Scientific Experts

  • Luke H Herbertson
  • Keefe B Manning
  • Steven Deutsch
  • Kwanghyun Sohn
  • John M Tarbell
  • Arnold A Fontaine
  • T Michael Przybysz

Detail Information

Publications5

  1. ncbi Near field flow characteristics of the Bjork-Shiley Monostrut valve in a modified single shot valve chamber
    Keefe B Manning
    Department of Bioengineering, The Pennsylvania State University, University Park 16802, USA
    ASAIO J 51:133-8. 2005
    ..This study provides further evidence that stable bubble formation may stem from the intense vortex cavitation occurring during valve closure and rebound...
  2. ncbi Acoustic and visual characteristics of cavitation induced by mechanical heart valves
    Kwanghyun Sohn
    The Pennsylvania State University, Department of Bioengineering, 205 Hallowell Building, University Park, PA 16802, USA
    J Heart Valve Dis 14:551-8. 2005
    ..CONCLUSION: The use of the peak pressure may be the preferred method for correlating cavitation intensity in structures for which the separation of valve closure noise and cavitation signal is difficult, as for the valves studied here...
  3. ncbi The effect of dissolved carbon dioxide on cavitation intensity in mechanical heart valves
    Luke H Herbertson
    Department of Bioengineering, The Pennsylvania State University, University Park, PA 16802, USA
    J Heart Valve Dis 14:835-42. 2005
    ..Therefore, the role of CO2 is limited to stable bubble development...
  4. ncbi Wavelet transforms in the analysis of mechanical heart valve cavitation
    Luke H Herbertson
    Department of Bioengineering, The Pennsylvania State University, University Park, PA 16802, USA
    J Biomech Eng 128:217-22. 2006
    ..The overall goal of this work is to eventually link specific valves with characteristic waveforms or distinct types of cavitation, thus promoting improved valve designs...
  5. ncbi Modifying a tilting disk mechanical heart valve design to improve closing dynamics
    Luke H Herbertson
    Department of Bioengineering, The Pennsylvania State University, University Park, PA 16802, USA
    J Biomech Eng 130:054503. 2008
    ..Furthermore, the modified valve took longer to completely close than did the standard tilting disk valve, indicating a dampened impact and rebound of the occluder with its housing...